1. Field of the Invention
The present invention relates to a novel compound or a salt thereof having antifungal activity, a process for producing the same, and use thereof.
2. Background Art
Various diseases induced by fungi have seriously injured the health of human beings and non-human animals and have brought about serious damage to crops. For this reason, provision of compounds having antifungal activity and antifungal agents comprising these compounds as active ingredients and provision of advantageous processes for producing these compounds have always been desired in the art.
For example, some fungi are pathogenic to human beings and non-human animals and have been regarded as being responsible for fungal infectious diseases. The pathogenicity of fungi is on the whole weak. However, fungi often bring about grave condition in patients having lowered resistance thereto. This has led to an expectation of the development of novel pharmaceuticals useful for the treatment of these diseases. Some fungi are known as being pathogenic, and the development of novel antifungal agents for agricultural and gardening applications has been required associated with the control of plant diseases. Further, in reflection of recent housing circumstances, the invasion of filamentous fungi into housing has become an issue. In particular, the invasion of filamentous fungi often brings about such conditions as an allergy to human beings. The development of antifungal agents for preventing the occurrence of such symptoms, particularly the development of novel fungicides, has been desired in the art.
With a view to overcoming these problems, various antifungal agents have been developed with certain success.
However, the development of antifungal agents, which are not only environmentally friendly but also are safe against human beings and non-human animals and plants and are highly effective, has been desired in the art. Regarding agricultural and garden plants, the development of antifungal agents, which have high antifungal activity and excellent photostability, has been particularly desired.
On the other hand, Japanese Patent Laid-Open No. 233165/1995 discloses a part of compounds represented by formula (II). Compounds represented by formula (II) are generally referred to as “UK-2.”

wherein
R1 represents a straight-chain or branched saturated aliphatic hydrocarbon group or unsaturated aliphatic hydrocarbon group.
For example, Japanese Patent Laid-Open No. 233165/1995 discloses, in working examples, compounds represented by formula (II) wherein R1 represents isobutyryl (hereinafter referred to as “UK-2A”), compounds represented by formula (II) wherein R1 represents tigloyl (hereinafter referred to as “UK-2B”), compounds represented by formula (II) wherein R1 represents an isovaleryl group (hereinafter referred to as “UK-2C”), and compounds represented by formula (II) wherein R1 represents 2-methylbutanoyl (hereinafter referred to as “UK-2D”).
The above laid-open publications describe that UK-2 has antifungal activity and is useful as an active ingredient of antifungal agents for medical applications, fungicides for agricultural and gardening applications, and fungicides for industrial applications.
In particular, as compared with antimycins which likewise have a dilactone structure with a nine-membered ring and are represented by formula (III), UK-2 has the same or higher antimicrobial activity against fungi including yeasts, such as Candida, and filamentous fungi, such as Aspergillus, Penicillium, Mucor, Cladosporium, Rhizopus, Sclerotina, and Trichoderma, and has much lower cytotoxicity against culture cells, such as P388. Therefore, UK-2 has led to an expectation for usefulness thereof.

Further, the above laid-open publications describe the isolation of UK-2 as fermentation products from microorganisms belonging to Streptoverticillium.
Furthermore, “Tetrahedron Letters 39 (1998) 4363-4366”, discloses the synthesis of UK-2.